Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
An image forming apparatus such as a copier, a printer, and a facsimile, generally, includes a chassis structure that is formed by a frame structure made of sheet metal and includes a side plate frame. In the internal space of the chassis structure, a plurality of process units for performing an image formation process is arranged. The process units include, for example, a drum unit, which includes a photoreceptor drum configured to form a toner image and a developer unit, which supplies toner to the photoreceptor drum to form the toner image on the photoreceptor drum. A drive unit or a similar unit, which transmits driving power to rotated components (the photoreceptor drum or the developing roller or similar rotated components) included in the process units, is assembled to the side plate frame. This type of drive unit includes an array of a plurality of drive gears and a resin chassis that covers the array.
The resin chassis includes two plate-formed materials, and rotation shafts that each pivotally support the drive gears are arranged between the plate-formed materials. When the drive gear is rotated, a predetermined driving load is acting on the rotation shaft. There is provided a technique that causes a bearing to rotate in a predetermined timing not to concentrate loads in the same position of the bearing, which rotatably supports the rotation shaft.